Urea and/or thiourea-aldehyde-sulfite waste liquor condensation product



Patented Dec. 29, 1953 ac-S REFERENCE UREA AND/OR THIOUREA-ALDEHYDE-SUL-FITE WASTE LIQUOR CONDENSATION PRODUCT Ralph E. Plump, Pittsfield,Mass., and James W. Carroll, Lafayette Hill, Pa., assignors to ThePennsylvania Salt Manufacturing Company, Philadelphia, Pa., acorporation of Pennsylvania No Drawing. Application February 11, 1950,

- Serial No. 143,822

3 Claims. (Cl. 26017.5)

This invention relates to metal pickling and to new compositionsparticularly useful in this field, the present application being acontinuation in part of application No. 645,235, filed February 2, 1946,and now abandoned.

In the pickling of metals, i. e. removal of scale or other metaloxidation products from metal surfaces, it is customary to treat themetal with a dilute aqueous solution of a relatively strong acid such assulfuric or hydrochloric acid. In prior art practices, a compound orcgmpounds which exhibit inhibiting pro erties are usually incorporamflmgiigfidin an effort to lessen the attack on the metal. For example,various w lla? PXpi DMLdQKQIlLEiEflLQQwna-lso: l 1 o1ic stillresiduesxarnmatiathionreaderblaiiyes, d. sifti nmmdrsiso c arywhiwmasand an aldehyde baxelqe a ediahareinbihie ingproperties. It has alsobeen suggested heretofore that the addition of such materials ascellulose pulp waste liquor and gelatin may increase the efliciencies ofsome pickling baths.

We have now discovered that the solid condensation products obtained byreacting urea, thiourea, or a mixture of urea and thiourea with amixture of acidified sulfite pulp waste liquor and a water-solublealdehyde in the presence of an acid catalyst exhibit markedly improvedin hibiting properties against metal attack by acid pickling bathsggntainingnon-oxidizing aci s as compared to prior art products.

Though we do not wish to be limited by any theoretical explanation, itis believed that the surprisingly superior inhibiting properties of theproducts obtained may be attributed in part to a reaction in addition tothe expected condensation of urea or thiourea with aldehyde, namely achemical reaction between at least some of the constituents of thesulfite pulp waste liquor and one or more of the other constituents.I'he composition of sulfite pulp waste liquor varies somewhat with thesource and treatment, but usually consists of some inorganic materialssuch as calcium sulfate, calcium oxide and water, thio acids, otheracids, chiefly lignosulfonic acid and their calcium salts, lignin,dextrose, mannose, gums, albumins, resins, vanillin and fermentablesugars. Of these the more important constituents are believed to belignosulfonic acid, lignin, dextrose, mannose and vanillin. Whatever theexplanation, we have found the product of the above described reactionis markedly superior in metal pickling inhibiting properties to amixture of the components, considered individually or in any combinationthereof, e. g. a mixture of ureaof thiourea-aldehyde condensationproduct and sulfite pulp waste liquor. Thus, in a typical instance, wefound that a urea-formaldehyde-sulfite waste liquor product madeaccording to our invention gave almost 50% increased metal protection ascompared to equivalent quantities of a mixture of sulfite pulp waste anda urea-formaldehyde condensation product. Excellent results are achievedon metals such as various types of steels, iron, stainless steel, tinnedsteel, tinned copper, and tin.

In general, we incorporate our new condensation product in a picklingbath of thetype customarily employed for cleaning metal objects, usuallyan aqueous solution containing from 1 to 50% by weight of a relativelystrong nonoxidizing inorganic acid such as sulfuric, phosphoric,hydrochloric or hydrofluoric acid, preferably in 5-20% by weightsulfuric acid or 5-30% hydrochloric acid. In some instances beneficialresults may be achieved by incorporating our condensation product inaqueous mixtures of these and other acids. Furthermore, we have foundthat our new product may advantageously be admixed with other materialsknown to aid or exhibit inhibiting properties; for example, glue,

sodium chloride and diphenylthiourea may be admixed therewith.

As illustrative of a method of preparing our condensation product, wemix urea, thiourea, or both, with sulfite pulp waste liquor and awatersoluble aldehyde in an acid reaction medium; Thus, urea and/orthiourea may be dissolved in water and the other two reactants addedthereto. The resulting mixture may then be acidified and the precipitatewhich forms separated and dried. In preparing the condensation productsof our present invention the sulfite pulp waste liquor used shouldpreferably not contain more than 30 grams llgnone (i. e. 15 grams of thetotal solids of the waste liquor) per 15 grams urea, thiourea ormixtures of urea and thiourea employed i. e., more than 1 gram totalsolids of sulfite pulp waste liquor per gram urea, thiourea or mixturesthereof. If higher concentrations are used, the acid inhibitingproperties of the resulting product are found to be unsatisfactory. Wehave obtained the best results by using, in the condensation reaction,sulfite pulp waste liquor concentrations of about 2.5 grams lignone(1.25 grams solid waste liquor) per 15 grams of urea and/or thiourea.However, considerably lower concentrations of the sulfite pulp wasteliquor can be employed, excellent acid inhibiting materials beingobtained when concentrations as low as 0.5

ENUVI l H ER Variation of sulfite pulp waste liquor "(tigno'nmconcentration HCl catalyst Thio- Forme- Lig- Weight Percent urea, lin,none, yield, protec-. grams grams grams grams percent 'tion "Theproduct, prepared according to our invention, is incorporated in atypical acid pickling bath, either alone or'in conjunction with othermaterials which are known to exhibit inhibiting properties. Acomparatively low concentration of 'our inhibitor is sufiicient toobtain good metal protection. The concentration required to achieve acertain amount of metal protection will vary with the picklingconditions, but the quantity required'is significantly lower than thatof heretofore known inhibiting materials. Thus, we have found that aconcentration, in acid baths of 5 to 10% acid, or as little as 0.001% byweight is effectiveunder usual pickling conditions while about 0.025% byweight is the usual preferred concentration, and 0.10% is the usualmaximum "amount'nec'es'sary, though more may be used, 7 being about themaximum amount which will dissolve in the acid pickling'bath.

To illustrateour method of preparation by a "specific example, we maydissolve "60 parts of urea and 6 parts of thiourea in 89 parts of water.89 parts of sulfite pulp waste liquor (containirig about 12% solids) and89 parts of 37% formaldehydeare added and the solution stirred.Alternatively, a concentrated sulfite pulp waste liquor may be used witha corresponding addition of water. 15 parts of hydrochloric acid areadded with stirring. A precipitate soon forms which may be separated andwashed with water, followed by oven drying at 100 C. The product soobtained is superior in inhibiting properties to those of the prior art,and may be admixed with other materials'of inhibiting value,-such asdiphenylthiourea, glue, etc. TO-obtain a preferred "product we 'admix:45%of our condensation product prepared as described above.

9%. e 19% sodium chloride.

7 15 'diphenylthiourea.

found that the condensation reaction product will have superior acidinhibiting properties as long as a water-soluble aldehyde, having lessthan two functional groups other than the aldehyde group is used, thealdehyde to urea and/or thiourea ratio of the reaction mixture ismaintained to within 0.1 to 5 mols aldehyde per mol of urea and/orthiourea, and the concentration of the sulfite pulp waste liquor doesnot exceed 30 grams Lignone, or 15 grams solid waste liquor, per 15grams of urea and/or thiourea employed. The table of Example 2, whichgives some of the reaction ratios employed, helps further to illustratethe wide range of urea and/or thiourea reactants to aldehyde reactantsthat can be employed while practicing our invention. In studying thistable, it should be kept in mind that the Lignone can be varied, asillustrated in Example 1, for-each ratio of urea and/or thiourea toaldehyde given in Example 2. However, for ease of illustration, theamount of urea and thiourea reactants of Example -1 has been keptconstant whereas the amount of Lignone present in the reactants ofExample 2 has been kept constant. The resulting product of each of thereaction ratios given in Example 2 was found on testing to be anexcellent acid inhibitor. The tests were carried out in the same manneras described ior Example 1.

EXAMPLE 2 T Li no e.

' grams Urea and'thiouremmols Aldehyde, mols 0. 5 formaldehyde 0.1formaldehyde l benzaldehyde 5 butyraldehyde 0. 33 butyraldehyde. 1formaldehyde 5 formaldehyde 0. 125 formaldehyde...

In the following examples, which illustrate but do not limit ourinvention, the composition of the specific example set forth on page 5was used, and is designated therein simply as the 'inhibitor. The lossin weight of the metal after pickling with and without the presence ofthe inhibitor gives the percent protectionaccor'ding to the expression:

(Weight loss uniuhibited)(Wcight loss inhibited) mo (Weight lossuninhibited) x These data were obtained by pickling-at varioustemperatures strips of cold rolled 'steel in' baths of 6% hydrochloricacid containing-the indicated quantities of inhibitor:

Percentprbttion Inhibitor concentration"(welghtpercent) 76. 2 8120 A 79.s -s4.-2 s1, 5 i 87. 4 -84.-8 :96. 4 90. 0 --97. 4

' EXAMPLE 4 These data'were obtained by pickling at 80 C. strips of'difierent-steels in; bathsof 10% sulfuric acid containing the indicatedquantities of inhibitor:

Percent protection at the in- These data were obtained by pickling, at25 or 50 C. strips of steel in hydrofluoric acid baths containingvarious quantities of inhibitor:

Percent protection Inhibitor concentration (weight percent) EXAMPLE 6This example shows the excellent metal protection properties of ourproducts when used in relatively high strength hydrofluoric acidpickling baths, and also demonstrates high stability and long lastingqualities. These data were obtained by pickling, at 24 0., steel stripsin a bath of 60% hydrofluoric acid containing 0.50% by weight of ourinhibitor for the period of time indicated:

Percent Time hours protection tied asses @0006 Similar picklingoperations were carried out employing inhibitor compositions made fromurea in the absence of thiourea, from thiourea without urea present, andfrom mixtures of urea and thiourea other than the above-describedmixtures, and marked improvement in metal protection was noted in eachcase. Similarly, aldehydes other than formaldehyde. e. g. acetaldehyde,propionaldehidefbutyraldehyde, benzaldehyde or aldghmay be employed inthe condensation reaction, and considerable modification is possible inthe choice of materials to be admixed with our condensation productswithout departing from our invention.

Having thus described our invention, we claim:

1. A new composition of matter comprising the condensation productresulting from an acidified reaction mixture of sulfite pulp wasteliquor, water-soluble aldehyde, urea and thiourea in which reactionmixture 0.1 to 5 mols of aldehyde are present per mol of combined ureaand thiourea and said sulfite pulp waste liquor contains no more than 1gram of sulfite pulp waste liquor solids per gram of combined urea andthiourea.

2. A new composition of matter comprising the condensation productresulting from an acidified reaction mixture of sulfite pulp wasteliquor,-

water-soluble aldehyde, and urea in which reaction mixture 0.1 to 5 molsof aldehyde are present per mol of urea and said sulfite pulp wasteliquor contains no more than 1 gram or sulfite pulp waste liquor solidsper gram of urea. 3. A new composition of matter comprising thecondensation product resulting from an acidified reaction mixture ofsulfite pulp waste liquor, water-soluble aldehyde, and thiourea in whichreaction mixture 0.1 to 5 mols of aldehyde are present per mol ofthiourea and said sulfite pulp waste liquor contains no more than 1 gramof sulfite pulp waste liquor solids per gram or thiourea. RALPH E.PLUMP. JAMES W. CARROLL.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,807,711 Schmidt June 2, 1931 2,266,265 Rieche et a1. Dec.16, 1941 2,321,451 Bauer June 8, 1943 2,369,613 Schubert Feb. 13, 19452,387,619 Seidel Oct. 23, 1945 2,405,650 Hartwig Aug. 13, 1946 FOREIGNPATENTS Number Country Date 74,383 Norway Dec. 6, 1948

1. A NEW COMPOSITION OF MATTER COMPRISING THE CONDENSATION PRODUCTRESULTING FROM AN ACIDIFIED REACTION MIXTURE OF SULFITE PULP WASTELIQUOR, WATER-SOLUBLE ALDEHYDE, UREA AND THIOUREA IN WHICH REACTIONMIXTURE 0.1 TO 5 MOLES OF ALDEHYDE ARE PRESENT PER MOL OF COMBINED UREAAND THIOUREA AND SAID SULFITE PULP WASTE LIQUOR CONTAINS NO MORE THAN 1GRAM OF SULFITE PULP WASTE LIQUOR SOLIDS PER GRAM OF COMBINED UREA ANDTHIOUREA.